Low-noise amplifier and circuit for controlling the same

• US 6,144,259 A
• Filed: 03/18/1999
• Issued: 11/07/2000
• Est. Priority Date: 03/18/1998
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kirisawa, Akihiro
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Choe, Henry
• Application Number:
  US09/271,530
• Time in Patent Office: 600 Days
• Field of Search: 330/277, 330/296, 330/298, 330/302, 455/78, 455/84, 455/83, 455/573, 455/575
• US Class Current: 330/296
• CPC Class Codes: H03F 1/301 in MOSFET amplifiers H03F1/303, H03F1/305, H03F1/308 take precedence
• CPC Class Codes: H03F 1/52 Circuit arrangements for protecting such amplifiers monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier

Abstract

A circuit for controlling a low-noise amplifier includes a low-noise transistor as an amplifying device. A bias voltage controller decreases a voltage to be applied to a gate of the transistor down to a voltage equal to or smaller than a pinch-off voltage to thereby pinch-off the low-noise amplifier, while power to be provided to the low-noise amplifier is kept off. In accordance with the circuit, even if an excessive input signal is input into the low-noise amplifier while the low-noise amplifier is not in operation, a gate current does not run through a transistor constituting the low-noise amplifier. Hence, it is possible to prevent destruction of a device and reduction in reliability of a device. In other words, the circuit operates as a circuit for protecting a device.

Claims

1. A circuit for controlling a low-noise amplifier including a low-noise transistor as an amplifying device, said circuit comprising:

a bias voltage controller which varies a bias voltage to be applied to a gate of said transistor while said low-noise amplifier is not in operation;

wherein;

said bias voltage controller is comprised of first to fifth resistors, and first and second bipolar transistors;

said first bipolar transistor being electrically connected at a base thereof to said first resistor, being electrically connected at an emitter thereof to a positive voltage source, and being electrically connected at a collector thereof to said second resistor, said emitter being electrically connected to said base through said third resistor;

said second bipolar transistor being electrically connected at a base thereof to a node between said collector of said first bipolar transistor and said second resistor, said second bipolar transistor being grounded at an emitter thereof, and being electrically connected at a collector thereof to a negative voltage source through said fourth and fifth resistors.

2. A circuit for controlling a low-noise amplifier including a low-noise transistor as an amplifying device, said circuit comprising:

a bias voltage controller which varies a bias voltage to be applied to a gate of said transistor while said low-noise amplifier is not in operation;

wherein;

said bias voltage controller is comprised of first to fourth resistors and a MOS field effect transistor;

said MOS field effect transistor being electrically connected at a gate thereof to said first resistor and to a voltage source through said second resistor, said MOS field effect transistor being grounded at a drain thereof, and being electrically connected at a source thereof to said voltage source through said third and fourth resistors.

3. A circuit for controlling a low-noise amplifier including a low-noise transistor as an amplifying device, said circuit comprising:

a bias voltage controller which decreases a voltage to be applied to a gate of said transistor down to a voltage equal to or smaller than a pinch-off voltage to thereby pinch-off said low-noise amplifier, power provided to said low-noise amplifier is kept off;

wherein;

said bias voltage controller is comprised of first to fifth resistors, and first and second bipolar transistors;

said first bipolar transistor being electrically connected at a base thereof to said first resistor, being electrically connected at an emitter thereof to a positive voltage source, and being electrically connected at a collector thereof to said second resistor, said emitter being electrically connected to said base through said third resistor;

said second bipolar transistor being electrically connected at base thereof to a node between said collector of said first bipolar transistor and said second resistor, said second bipolar transistor being grounded at an emitter thereof, and being electrically connected at a collector thereof to a negative voltage source through said fourth and fifth resistors.

4. A circuit for controlling a low-noise amplifier including a low-noise transistor as an amplifying device, said circuit comprising:

a bias voltage controller which decreases a voltage to be applied to a gate of said transistor down to a voltage equal to or smaller than a pinch-off voltage to thereby pinch-off said low-noise amplifier, when power provided to said low-noise amplifier is kept off;

wherein;

said bias voltage controller is comprised of first to fourth resistors and a MOS field effect transistor;

said MOS field effect transistor being electrically connected at a gate thereof to both said first resistor and to a voltage source through said second resistor, said MOS field effect transistor being grounded at a drain thereof, and being electrically connected at a source thereof to said voltage source through said third and fourth resistors.

5. A mobile communication terminal comprising:

an antenna which receives radio signals;

a first amplifier which amplifies said radio signals thereby producing amplified radio signals;

a first circuit which processes said amplified radio signals;

a second circuit which produces other radio signals to be transmitted through said antenna;

a second amplifier which amplifies said other radio signals;

a duplexer which transmits said radio signals from said antenna to said first amplifier and which transmits said other radio signals from said second amplifier to said antenna; and

a bias voltage controller electrically connected to both said first and second amplifiers, said bias voltage controller varies a bias voltage to be applied to a gate of a transistor of said first amplifier, when said first amplifier is not in operation;

wherein;

said bias voltage controller is comprised of first to fifth resistors, and first and second bipolar transistors;

said first bipolar transistor being electrically connected at a base thereof to said first resistor, being electrically connected at an emitter thereof to a positive voltage source, and being electrically connected at a collector thereof to said second resistor, said emitter being electrically connected to said base through said third resistor;

said second bipolar transistor being electrically connected at a base thereof to a node between said collector of said first bipolar transistor and said second resistor, said second bipolar transistor being grounded at an emitter thereof, and being electrically connected at a collector thereof to a negative voltage source through said fourth and fifth resistors.

6. A mobile communication terminal comprising:

an antenna which receives radio signals;

a first amplifier which amplifies said radio signals thereby producing amplified radio signals;

a first circuit which processes said amplified radio signals;

a second circuit which produces other radio signals to be transmitted through said antenna;

a second amplifier which amplifies said other radio signals;

a duplexer which transmits said radio signals from said antenna to said first amplifier and which transmits said other radio signals from said second amplifier to said antenna; and

a bias voltage controller electrically connected to both said first and second amplifiers, said bias voltage controller varies a bias voltage to be applied to a gate of a transistor of said first amplifier, when said first amplifier is not in operation;

wherein;

said bias voltage controller is comprised of first to fourth resistors and a MOS field effect transistor;

said MOS field effect transistor being electrically connected at a gate thereof to said first resistor and to a voltage source through said second resistor, said MOS field effect transistor being grounded at a drain thereof, and being electrically connected at a source thereof to said voltage source through said third and fourth resistors.

7. A mobile communication terminal comprising:

an antenna which receives radio signals;

a first amplifier which amplifies said radio signals to produce amplified radio signals;

a first circuit which processes said amplified radio signals;

a second circuit which produces other radio signals to be transmitted through said antenna;

a second amplifier which amplifiers said other radio signals;

a duplexer which transmits said radio signals from said antenna to said first amplifier and which transmits said other radio signals from said second amplifier to said antenna; and

a bias voltage controller electrically connected to both said first and second amplifiers, said bias voltage controller decreases a voltage to be applied to a sate of a transistor of said first amplifier down to a voltage equal to or smaller than a pinch-off voltage to thereby pinch-off said first amplifier, when power provided to said first amplifier is kept off;

wherein said bias voltage controller is comprised of first to fifth resistors, and first and second bipolar transistors;

said first bipolar transistor being electrically connected at a base thereof to said first resistor, being electrically connected at an emitter thereof to a positive voltage source, and being electrically connected at a collector thereof to said second resistor, said emitter being electrically connected to said base through said third resistor;

said second bipolar transistor being electrically connected at a base thereof to a node between said collector of said first bipolar transistor and said second resistor, said second bipolar transistor being grounded at an emitter thereof, and being electrically connected at a collector thereof to a negative voltage source through said fourth and fifth resistors.

8. A mobile communication terminal comprising:

an antenna which receives radio signals;

a first amplifier which amplifies said radio signals to produce amplified radio signals;

a first circuit which processes said amplified radio signals;

a second circuit which produces other radio signals to be transmitted through said antenna;

a second amplifier which amplifiers said other radio signals;

a duplexer which transmits said radio signals from said antenna to said first amplifier and which transmits said other radio signals from said second amplifier to said antenna; and

a bias voltage controller electrically connected to both said first and second amplifiers, said bias voltage controller decreases a voltage to be applied to a gate of a transistor of said first amplifier down to a voltage equal to or smaller than a pinch-off voltage to thereby pinch-off said first amplifier, when power provided to said first amplifier is kept off;

wherein said bias voltage controller is comprised of first to fourth resistors and a MOS field effect transistor;

said MOS field effect transistor being electrically connected at a gate thereof to said first resistor and to a voltage source through said second resistor, said MOS field effect transistor being grounded at a drain thereof, and being electrically connected at a source thereof to said voltage source through said third and fourth resistors.

9. A low-noise amplifier comprising:

an amplifying device comprised of a low-noise transistor; and

a bias voltage controller which varies a bias voltage to be applied to a gate of said transistor while said amplifying device is not in operation;

wherein;

said bias voltage controller is comprised of first to fifth resistors, and first and second bipolar transistors;

said first bipolar transistor being electrically connected at a base thereof to said first resistor, being electrically connected at an emitter thereof to a positive voltage source, and being electrically connected at a collector thereof to said second resistor, said emitter being electrically connected to said base through said third resistor;

said second bipolar transistor being electrically connected at a base thereof to a node between said collector of said first bipolar transistor and said second resistor, said second bipolar transistor being grounded at an emitter thereof, and being electrically connected at a collector thereof to a negative voltage source through said fourth and fifth resistors.

10. A low-noise amplifier comprising:

an amplifying device comprised of a low-noise transistor; and

a bias voltage controller which varies a bias voltage to be applied to a gate of said transistor while said amplifying device is not in operation;

wherein;

said bias voltage controller is comprised of first to fourth resistors and a MOS field effect transistor;

said MOS field transistor being electrically connected at a gate thereof to said first resistor and to a voltage source through said second resistor, said MOS field effect transistor being grounded at a drain thereof, and being electrically connected at a source thereof to said voltage source through said third and fourth resistors.

11. A low-noise amplifier comprising:

an amplifying device comprised of a low-noise transistor; and

a bias voltage controller which decreases a voltage to be applied to a gate of said transistor down to a voltage equal to or smaller than a pinch-off voltage to thereby pinch-off said amplifying device, when power provided to said amplifying device is kept off;

wherein;

said bias voltage controller is comprised of first to fifth resistors, and first and second bipolar transistors;

said first bipolar transistor being electrically connected at a base thereof to said first resistor, being electrically connected at an emitter thereof to a positive voltage source, and being electrically connected at a collector thereof to said second resistor, said emitter being electrically connected to said base through said third resistor;

said second bipolar transistor being electrically connected at a base thereof to a node between said collector of said first bipolar transistor and said second resistor, said second bipolar transistor being grounded at an emitter thereof, and being electrically connected at a collector thereof to a negative voltage source through said fourth and fifth resistors.

12. A low-noise amplifier comprising:

an amplifying device comprised of a low-noise transistor; and

a bias voltage controller which decreases a voltage to be applied to a gate of said transistor down to a voltage equal to or smaller than a pinch-off voltage to thereby pinch-off said amplifying device, when power provided to said amplifying device is kept off;

wherein;

said bias voltage controller is comprised of first to fourth resistors and a MOS field effect transistor;

said MOS field effect transistor being electrically connected at a gate thereof to said first resistor and to a voltage source through said second resistor, said MOS field effect transistor being grounded at a drain thereof, and being electrically connected at a source thereof to said voltage source through said third and fourth resistors.